What electrical standards apply to factory installations in the UK?

Factory electrical installations must comply with BS 7671:2018+A4:2026 (the IET Wiring Regulations) as the primary electrical installation standard, and the Electricity at Work Regulations 1989 as the primary statutory instrument. Where hazardous areas exist, DSEAR 2002 (implementing the ATEX Directive) applies to zone classification and the selection of equipment for use in those zones. The Health and Safety at Work etc. Act 1974 also places general duties on employers for the safe management of electrical systems. For specific types of factory equipment, additional product standards such as BS EN 60204-1 (Safety of Machinery — Electrical Equipment of Machines) apply.

What is a Motor Control Centre (MCC) and when is one required?

A Motor Control Centre (MCC) is a factory-assembled switchboard containing motor starters, variable frequency drives (VFDs), protective devices, and control equipment for a group of electric motors or other electrical loads. MCCs are used in factories where multiple motors are controlled from a centralised location, such as pump stations, HVAC plant rooms, conveyor systems, and process lines. They are built to BS EN 61439-2 (Low-voltage switchgear and controlgear assemblies) and factory-tested before delivery. MCCs provide a safer, more maintainable arrangement than individually mounted starters and allow motor data to be integrated into SCADA and BMS systems.

What is power factor correction and why is it important in factories?

Power factor is the ratio of active power (kW, which does useful work) to apparent power (kVA, drawn from the supply). Motor-heavy factory installations typically have a power factor of 0.7 to 0.85 lagging due to the inductive nature of motor windings. A low power factor means the utility supply must deliver more current than strictly necessary to provide the required active power, resulting in higher cable losses, larger cable and switchgear sizes, and utility reactive power charges. Power factor correction is achieved by installing capacitor banks (fixed or automatically switched) to supply reactive power locally, improving the power factor at the point of metering to typically 0.95 or above and eliminating reactive power charges.

What IP rating is required for electrical equipment in factories?

The Ingress Protection (IP) rating required for factory electrical equipment depends on the specific environment. BS EN 60529 defines the IP rating system. For general factory floors with dust and splashing water, IP54 is commonly specified for enclosures and motors. Wet areas such as food processing or wash-down areas require IP65 or IP66 (dust-tight, strong jet water protection). Submerged pump applications require IP68. Outdoor equipment typically requires IP55 as a minimum. Within the factory office or control room, IP20 or IP21 may be adequate. The IP rating must be selected to match the actual environmental conditions at each specific location.

What are ATEX zones and how do they affect electrical installation in factories?

ATEX zone classification under DSEAR 2002 identifies areas of a factory where flammable gases, vapours, mists, or dusts may be present in sufficient quantities to present an explosion risk. Zone 0 (or Zone 20 for dust) is where an explosive atmosphere is present continuously or for long periods. Zone 1 (Zone 21) is where it is likely to occur in normal operation. Zone 2 (Zone 22) is where it is not likely to occur in normal operation but may occur occasionally. All electrical equipment installed in an ATEX zone must be selected and installed in accordance with BS EN 60079 (for gases) or BS EN 60079-10-2 (for dusts), must carry the Ex marking, and must be appropriate for the specific zone category and gas/dust group.

How are HRC fuses different from standard MCBs in factory applications?

High Rupturing Capacity (HRC) fuses to BS 88 are current-limiting devices that can interrupt extremely high fault currents (up to 80 kA or more) very rapidly, typically within one half-cycle. In a factory with a large transformer and short cable runs to the distribution board, the prospective short-circuit current can be very high — potentially exceeding the rated breaking capacity of standard miniature circuit breakers (MCBs). HRC fuses provide reliable protection at these high fault levels without the risk of rupture or damage to the switchboard. They also provide time-current characteristics (particularly in the HRC type gG and aM categories) well suited to motor starting, where the initial inrush current is 6 to 8 times the full-load current.

What cable management systems are typical in UK factory electrical installations?

Factory cable management typically uses a combination of: cable trays (perforated or ladder type) in ceiling voids and along structural steelwork for power distribution cables; cable trunking for control and instrumentation cables in plant rooms and along walls; conduit (steel or PVC) for final connections to individual machines, luminaires, and sockets where mechanical protection is required; and mineral-insulated copper-clad (MICC) or fire-resistant cables for essential circuits and circuits in high-temperature environments. Cable routes should be designed to maintain segregation between power and data/control cables (minimum 300mm separation without screening) to prevent electromagnetic interference.

INDUSTRIAL ELECTRICAL GUIDE

Factory Electrical Installation UK: Industrial Wiring Guide

The complete technical guide to factory electrical installation in the UK — covering three-phase supplies, motor control centres, power factor correction, HRC fuses, IP ratings for industrial environments, ATEX zone classification, and cable management.

Start 7-day free trial

Free for 7 days · No charge until day 8 · Cancel anytime · Used by 1,000+ UK electricians

14 min readUpdated 2026-06-10Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

ShareX in W

1,000+

UK electricians

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer — DP Electrical

Key Takeaways

1Factory electrical installations in the UK must comply with BS 7671:2018+A4:2026, the Electricity at Work Regulations 1989, and where applicable, the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) for ATEX hazardous area classification.
2Three-phase 400V TN-S or TN-C-S supplies are standard for factory installations. Large motor loads may require a dedicated high-fault-level supply with appropriate switchgear rated for the available prospective short-circuit current.
3Motor control centres (MCCs) consolidate motor starters, variable frequency drives, protective relays, and power factor correction equipment into a structured, maintainable enclosure. MCCs in factories are designed and built to BS EN 61439.
4HRC (High Rupturing Capacity) fuses to BS 88 are specified in factory environments where high fault levels demand fast, reliable protection that current limiting MCBs may not provide.
5The Electricity at Work Regulations 1989 require all persons working on or near factory electrical systems to be competent for the work they carry out. Regulation 4(3) specifically requires live working to be prevented where possible.

01 · Industrial Electrical Guide

Factory Electrical Installation in the UK

Factory electrical installation encompasses the design, installation, and maintenance of electrical systems in manufacturing, processing, and industrial production facilities. The complexity of factory installations ranges from light engineering workshops with single-phase supplies to heavy process plants requiring high-voltage distribution, large motor drives, and sophisticated control systems.

Factory installations present unique challenges that are not found in commercial or domestic work: high fault currents from large transformers, significant motor loads with inrush current demands, harsh environmental conditions requiring appropriate IP protection, potential ATEX hazardous areas, and 24/7 operational requirements that constrain maintenance windows. The Electricity at Work Regulations 1989 impose strict duties on factory occupiers to maintain safe electrical systems.

Key standards: BS 7671:2018+A4:2026, Electricity at Work Regulations 1989, DSEAR 2002 (ATEX), BS EN 61439 (switchgear assemblies), BS EN 60204-1 (machine electrical equipment), BS EN 60529 (IP ratings).
Competence requirement: The Electricity at Work Regulations 1989 Regulation 16 requires that no person shall engage in work on electrical systems unless they are competent to prevent danger or injury from the work. Industrial electrical installation is a high-risk activity requiring appropriate qualifications and experience.

Free download

Get the BS 7671 A4:2026 Cheat Sheet — free

Every key change in the 2026 amendment on one page. AFDDs, TN-C-S protection, new schedule columns, model forms. Pinned on your van dash.

Every regulation change summarised
New model forms (EIC + MEIWC)
Free PDF — no subscription

02 · Industrial Electrical Guide

Three-Phase Supplies in Factory Installations

The majority of factory electrical power is distributed as three-phase 400V AC. Three-phase supplies are required for most industrial motor loads and are more efficient than single-phase for high-power applications, using less conductor material for the same power transfer.

HV/LV transformers: Most factories receive an 11kV (or 33kV) HV supply from the utility network, transformed to 400V LV by a dedicated on-site transformer. Common transformer ratings for factory use range from 315 kVA to 2,500 kVA. The transformer impedance and rating determine the available prospective short-circuit current at the LV terminals.
TN-S earthing: Factory installations commonly use TN-S earthing with a separate PE conductor throughout. This minimises earth fault loop impedance, allowing fast disconnection by overcurrent protective devices, and keeps the neutral conductor free from earth fault current. Where TN-C-S supply is used, the PME earth should be segregated from sensitive control and instrumentation circuits.
Phase balance: Single-phase loads (lighting, small power) in factories must be distributed evenly across all three phases to maintain balance. A phase imbalance exceeding 5 per cent at the main switchboard causes overheating of three-phase motor windings, increased neutral current, and transformer inefficiency.
Voltage drop: Cable sizing for factory circuits must ensure voltage drop stays within the limits of BS 7671 Appendix 4 (Section 6.4). For motor circuits, excessive voltage drop can prevent the motor starting under load and cause overheating. A maximum voltage drop of 5 per cent from the origin to the point of use is a typical design requirement for industrial motor circuits.

03 · Industrial Electrical Guide

Motor Control Centres (MCCs)

A Motor Control Centre is a factory-assembled, type-tested switchboard that provides a centralised and structured approach to controlling and protecting groups of electric motors. MCCs are the standard solution in factories with more than a handful of motor loads.

Direct on-line (DOL) starters: The simplest motor starter. Connects the motor directly to the full supply voltage on starting. Suitable for small motors (typically up to 7.5 kW) where the starting current surge (typically 6 to 8 times full-load current) is acceptable to the supply system.
Star-delta starters: A traditional reduced-voltage starting method for motors above 7.5 kW. The motor starts connected in star (reducing starting current to approximately one-third of DOL) and transfers to delta when it approaches full speed. Requires a three-winding motor with six terminal connections.
Variable Frequency Drives (VFDs): Modern factories increasingly use VFDs (also called inverters or variable speed drives) for all but the simplest motor applications. VFDs provide smooth soft starting, precise speed control, significant energy savings at partial loads (fans and pumps can save 50 per cent or more), and reduced mechanical stress on driven equipment.
Motor protection: Each motor feeder within the MCC should include overload protection (electronic overload relay or thermal overload relay), short- circuit protection (HRC fuse or MCCB), phase failure protection, thermistor relay for motor winding temperature, and earth fault protection appropriate to the installation earthing system.

04 · Industrial Electrical Guide

Power Factor Correction in Factory Installations

Power factor correction (PFC) is one of the most cost-effective electrical improvements a factory can make. UK utility tariffs for industrial customers typically include a reactive power charge (sometimes expressed as a maximum demand charge or kVAr charge) when the power factor falls below 0.95 lagging.

Fixed capacitor banks: For loads that are relatively constant (base-load motors, transformers), fixed capacitor banks are connected permanently to the busbar. They provide a fixed reactive power injection and are the simplest and most reliable PFC option.
Automatic PFC panels: For factories with variable loads, automatic power factor correction (APFC) panels switch capacitor stages in and out as the load varies, maintaining the power factor within a target band (typically 0.95 to 0.99). A power factor controller monitors the busbar and operates contactors on individual capacitor banks.
Harmonic detuned filters: Factories with large VFD installations generate significant harmonic currents (5th, 7th, 11th harmonics). Plain capacitor banks can resonate with these harmonics, causing overheating and failure. Harmonic- detuned PFC uses reactors in series with each capacitor bank tuned to avoid resonance, typically at 189 Hz (detuning factor p = 7%).

05 · Industrial Electrical Guide

HRC Fuses and Circuit Breakers for Factory Installations

Protection device selection in factories must account for the potentially very high prospective short-circuit currents (PSCCs) available from large transformers, the high starting currents of motors, and the need for reliable discrimination between devices at different levels of the distribution hierarchy.

BS 88 HRC fuses: High Rupturing Capacity fuses to BS 88 are current-limiting devices capable of safely interrupting fault currents up to 80 kA. The gG (general purpose) type protects cables and equipment against overload and short-circuit. The aM (motor) type provides short-circuit protection only, designed to withstand motor starting surges without operation.
Moulded Case Circuit Breakers (MCCBs): MCCBs provide adjustable overcurrent protection and are resettable after operation. Industrial MCCBs are rated from 100A to 1,600A with breaking capacities of 25 kA to 150 kA. Electronic trip units allow separate adjustment of overload (Ir), short-time delay (Isd), and instantaneous (Ii) settings for precise discrimination.
Discrimination (selectivity): A fundamental requirement of factory distribution design is that a fault on any final circuit causes only the nearest upstream device to operate, leaving the rest of the distribution system energised. Discrimination must be verified by time-current characteristic overlays or manufacturer discrimination tables during the design stage.

Try Elec-Mate free for 7 days

16 certificate types, 70+ calculators, RAMS, quoting, invoicing, AI agents, and 46+ training courses — from £6.99/mo.

Start free trial

06 · Industrial Electrical Guide

IP Ratings for Industrial Environments

The Ingress Protection (IP) rating system defined in BS EN 60529 specifies the degree of protection provided by electrical enclosures against solid particles (first digit) and liquids (second digit). Selecting the correct IP rating for each location in a factory is essential for equipment longevity and safety.

IP44 — General factory: Protection against solid objects greater than 1mm and splashing water from any direction. Suitable for general factory floor areas with light dust and occasional water splashing.
IP54 / IP55 — Dusty or wet areas: IP54 provides dust protection (ingress not completely prevented but not enough to interfere with operation) and water jet protection. IP55 adds protection against low-pressure jets of water from any direction. Suitable for most factory floor environments.
IP65 / IP66 — Food & beverage / wash-down: IP65 is dust-tight and protects against low-pressure water jets. IP66 adds protection against powerful water jets. Required in food processing, pharmaceuticals, and any area subject to regular high-pressure wash-down with cleaning chemicals.
IK ratings: In addition to IP ratings, industrial enclosures in areas subject to mechanical impact (e.g. forklift traffic, vibration) should be specified with an IK impact protection rating to BS EN 62262. IK08 (5 joule impact resistance) is a common minimum for factory environments.

07 · Industrial Electrical Guide

ATEX Zone Classification in Factories

Factories that handle flammable gases, vapours, liquids, or combustible dusts must carry out an explosion risk assessment and zone classification under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). All electrical equipment installed in classified zones must be selected and installed in accordance with BS EN 60079 series.

Gas and vapour zones: Zone 0 (continuous presence), Zone 1 (likely in normal operation), Zone 2 (unlikely in normal operation). Common in paint spraying areas, fuel storage, solvent handling, and chemical processing.
Dust zones: Zone 20 (continuous), Zone 21 (likely in normal operation), Zone 22 (unlikely but possible). Common in grain handling, woodworking, plastics processing, and metal powder manufacturing.
Equipment selection: Ex-rated equipment must carry the Ex marking and be appropriate for the equipment category (1G, 2G, or 3G for gas; 1D, 2D, or 3D for dust) and gas group. Common protection concepts include flameproof enclosure (Ex d), increased safety (Ex e), intrinsic safety (Ex i), and pressurised enclosure (Ex p).
Installer competence: Installation, inspection, and maintenance of Ex-rated equipment requires specific competence. The CompEx scheme (Competency for Ex) provides the recognised UK qualification framework for hazardous area workers.

08 · Industrial Electrical Guide

Cable Management in Factory Installations

Effective cable management in a factory is essential for safety, maintainability, and future flexibility. Factory environments expose cables to mechanical damage, chemical attack, thermal stress, and electromagnetic interference, all of which must be considered in the cable management design.

Cable trays and ladders: Perforated cable tray or cable ladder is used for main distribution routes along structural steelwork. Cable ladder provides better support for heavy armoured cables. Tray fill should not exceed 40 per cent of the tray cross-section area to allow for heat dissipation and future additions.
Steel conduit: Steel conduit provides mechanical protection for cables in areas where impact or abrasion is likely, or where chemical exposure requires a robust enclosure. Hot-dip galvanised or stainless steel conduit is used in corrosive environments.
Segregation: Power cables (especially VFD output cables) generate high-frequency electromagnetic interference. A minimum separation of 300mm must be maintained between power and data/control cables, or segregation screens must be installed. VFD output cables should use screened cable with the screen earthed at both ends.
Cable selection: Armoured cables (SWA — Steel Wire Armoured) are standard for factory power distribution. The armour provides mechanical protection and can serve as the circuit protective conductor if suitably sized. XLPE insulation is specified for environments with elevated temperatures or where chemical resistance is required.

09 · Industrial Electrical Guide

For Electricians: Factory and Industrial Electrical Work

Factory and industrial electrical work is one of the most technically rewarding and well- remunerated specialisms in the UK electrical industry. The combination of complex systems, tight operational constraints, and high safety standards means that experienced industrial electricians are consistently in high demand.

Safe Isolation is Non-Negotiable

The Electricity at Work Regulations 1989 Regulation 13 requires that all electrical equipment shall be made dead before any work is carried out, unless it is unreasonable to do so. In factories this means following a formal safe isolation procedure: identify, isolate, secure, test, and earth. Never assume a circuit is dead without testing with an approved voltage indicator.

Certification and Documentation

All new factory electrical work must be certified with an Electrical Installation Certificate or Minor Works Certificate. Use the Elec-Mate certification app to complete all certificates and test schedules on site with instant PDF delivery to the factory maintenance team.

Manage factory electrical projects with Elec-Mate

Join 1,000+ UK electricians using Elec-Mate for on-site certification, quoting, and project management.

Try it free for 7 days

Frequently Asked Questions — Factory Electrical Installation

What electricians say

Verified reviews from the UK App Store.

One App for Everything!

Elec-Mate is my go to app for business and electrical work. It's feature rich without feeling cluttered. A true all in one app for quotes, certs, calculations, RAMS, EICRs, and more. I use it every day without fail, and it makes my workflow much smoother since I'm not jumping between apps anymore. The price-to-feature ratio is excellent. Any issues I've had, the developer responds within the hour and usually fixes them the same day. 100% recommend.

Fantastic app for electricians

I've used the app and the web based version for a while now and it's well worth the investment. If you're an apprentice or experienced Spark give it a go, you won't be disappointed.

Absolutely amazing

I've been using Elec-Mate for a while now, and honestly, it's one of the best apps I've ever downloaded. Every aspect of it feels thoughtfully designed, from the clean and intuitive interface to the powerful features that make everything so easy to manage. It's clear that a lot of care and attention went into building this app, and it shows in every detail.

Trusted by electricians across the UK

Real feedback from real sparks

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer

Sole Trader · DP Electrical

“I've won two contracts this month because I could turn quotes around same-day with the AI cost engineer.”

Nathan Perry

Electrician · NP Electrical Services

“The study centre got me through my AM2. Mock exams and flashcards are brilliant.”

Jake Pizey

3rd Year Apprentice · Apprentice

7-Day Free Trial — Cancel Anytime, No Hassle

Manage Your Factory Electrical Projects with Elec-Mate

Join 1,000+ UK electricians using Elec-Mate for on-site certification, quoting, and project management in industrial environments. 7-day free trial, cancel anytime.

“Replaced three separate apps with Elec-Mate. Certs, quotes, and scheduling all in one place.”

Daniel Palmer, DP Electrical

From £6.99/mo after trial — less than a coffee a week

or download the app

7 days free, then from £6.99/moCancel in one tap — no calls, no hassleiOS, Android & WebBS 7671 compliant

Factory Electrical Installation UK: Industrial Wiring Guide

Key Takeaways

Factory Electrical Installation in the UK

Get the BS 7671 A4:2026 Cheat Sheet — free

Three-Phase Supplies in Factory Installations

Motor Control Centres (MCCs)

Power Factor Correction in Factory Installations

HRC Fuses and Circuit Breakers for Factory Installations

Try Elec-Mate free for 7 days

IP Ratings for Industrial Environments

ATEX Zone Classification in Factories

Cable Management in Factory Installations

For Electricians: Factory and Industrial Electrical Work

Safe Isolation is Non-Negotiable

Certification and Documentation

Manage factory electrical projects with Elec-Mate

Frequently Asked Questions — Factory Electrical Installation

What electrical standards apply to factory installations in the UK?

What is a Motor Control Centre (MCC) and when is one required?

What is power factor correction and why is it important in factories?

What IP rating is required for electrical equipment in factories?

What are ATEX zones and how do they affect electrical installation in factories?

How are HRC fuses different from standard MCBs in factory applications?

What cable management systems are typical in UK factory electrical installations?

Continue reading

Warehouse Electrical Installation

Manufacturing Plant Electrical

Data Centre Electrical Installation

EICR Certificate App

Electrical Quoting App

What electricians say

One App for Everything!

Fantastic app for electricians

Absolutely amazing

Trusted by electricians across the UK

Manage Your Factory Electrical Projects with Elec-Mate